Fastening structure and fastening method

Abstract

Provided are a fastening structure and a fastening method capable of reinforcing a restraining force when two members are fastened by a fastening member without increasing the number of components, the structure comprising: a first fastened member 1 that is formed of an aluminum alloy; a second fastened member 2 that is formed of a metal material; and a bolt 3 (fastening member) that fastens and secures the fastened member 1 and the second fastened member 2 to each other. A plurality of grooves 4 intersecting a direction in which a sliding load is applied are provided in a fastening surface 1a of the first fastened member 1 facing the second fastened member 2. A plurality of protrusions 4c protruding toward the second fastened member 2 are formed at edges of the grooves 4, and the protrusions 4c contact the second fastened member 2 when fastened.

Description

Fastening structure and fastening method

[0001] The present invention relates to a fastening structure and a fastening method for fastening two members together with a fastening member.

[0002] Conventionally, there have been fastening structures for fastening two members, such as those that perform wet blasting on the fastening surfaces to roughen the fastening surfaces and form uneven surfaces to increase the binding force between the two members.Furthermore, there have also been structures that sandwich a thin layer containing silicon carbide between the two members and fasten them with bolts to increase the binding force between the two members (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2002-130223

[0004] However, in the above-mentioned Patent Document 1, a thin layer containing silicon carbide is sandwiched between two members, which increases the number of parts and makes the fastening process more time-consuming.

[0005] Therefore, the present invention aims to provide a fastening structure and fastening method that can strengthen the restraining force against external input when two members are fastened with a fastening member without increasing the number of parts.

[0006] In order to achieve the above-mentioned object, the fastening structure of the present invention comprises a first fastened member formed of an aluminum alloy, a second fastened member formed of a metal material, and a fastening member that fastens the first fastened member and the second fastened member together, and the fastening surface of the first fastened member facing the second fastened member has a plurality of grooves that intersect with the direction in which a sliding load is applied, and a plurality of protrusions that protrude toward the second fastened member are formed on the edges of the grooves, and the protrusions come into contact with the second fastened member when fastened.

[0007] Furthermore, the fastening method of the present invention is a method for fastening a first fastened member made of an aluminum alloy and a second fastened member made of a metal material together using a fastening member, and is characterized in that a plurality of grooves that intersect with the direction in which the sliding load is applied are formed on the fastening surface of the first fastened member facing the second fastened member by laser irradiation, and an axial force perpendicular to the fastening surface is applied to the first fastened member and the second fastened member by the fastening member.

[0008] According to the fastening structure and fastening method of the present invention, the contact area with the second fastened member can be secured by the multiple protrusions formed on the fastening surface of the first fastened member, thereby strengthening the restraining force against external input when two members are fastened with the fastening member without increasing the number of parts.

[0009] FIG. 3 is a side view of a fastening structure showing one embodiment of the present invention. FIG. 4 is an enlarged plan view showing the fastening surface of a first fastened member. FIG. 3 is a cross-sectional view taken along III-III in FIG. 2. FIG. 4 is an enlarged cross-sectional view showing a state in which a first fastened member and a second fastened member are fastened together. FIG. 5 is a graph comparing different materials of the second fastened member and different structures of the fastening surface. FIG. 6 is a schematic diagram showing an embodiment in which the present invention is applied to a knuckle for a vehicle. FIG. 7 is a schematic diagram showing another embodiment in which the present invention is applied to a compliance bracket for a vehicle.

[0010] 1 to 4 show an example of a fastening structure of the present invention, in which a first fastened member 1 made of an aluminum alloy and a second fastened member 2 made of a metal material, such as iron, are fastened together by a bolt 3 (the fastening member of the present invention).

[0011] The first fastened member 1 and the second fastened member 2 are members machined, for example, by a machining center (M / C), and the first fastened member 1 has a fastening surface 1a (machined surface) facing the second fastened member 1 formed with a plurality of grooves 4 by laser irradiation. As shown in Fig. 2, the grooves 4 have a plurality of first grooves 4a extending in the X-axis direction and a plurality of second grooves 4b extending in the Y-axis direction perpendicular to the X-axis direction. The first grooves 4a and the second grooves 4b are formed so as to intersect with the direction L in which a sliding load is applied by an external input F.

[0012] Furthermore, as shown in Figure 3, due to the molten burrs that are generated when forming the first groove portion 4a and the second groove portion 4b, multiple fine protrusions 4c that protrude toward the second fastened member 2 are formed on the edges of the first groove portion 4a and the second groove portion 4b.

[0013] The fastening surface 1a is divided into a plurality of divided surfaces 5 by the first grooves 4a and the second grooves 4b, and the divided surfaces 5 are formed uniformly and with regularity in the X-axis and Y-axis directions. The formation of the divided surfaces 5 makes the surface of the fastening surface 1a uneven, increasing its surface area. Furthermore, the edges of each divided surface 5 are surrounded by a plurality of protrusions 4c formed by molten burrs.

[0014] The first fastened member 1 and the second fastened member 2 thus formed are placed one on top of the other as shown in Figure 1, and bolts 3 are inserted through the bolt holes 1b formed in the first fastened member 1 and the bolt holes 2a formed in the second fastened member 2 to fasten them together, thereby applying a fastening axial force N perpendicular to the fastening surface 1a and fixing them in place.

[0015] When the first fastened member 1 and the second fastened member 2 are fastened together with the bolt 3, the fastening axial force N causes the protrusion 4c to come into contact with the second fastened member 2, as shown in Figure 4. This increases the slip resistance (restraining force against an external input F) regardless of the hardness of the second fastened member.

[0016] In other words, when the hardness of the second fastened member is higher than that of the first fastened member, the fastening axial force N causes the protrusion 4c to tilt inward, increasing the true contact area (friction coefficient) between the fastened members and increasing the slip resistance.

[0017] Furthermore, when the hardness of the second fastened member is lower than that of the first fastened member, the fastening axial force N causes the protrusion 4c to tilt inward, and the protrusion 4c digs into the second fastened member, thereby increasing the slip resistance due to the digging effect.

[0018] Furthermore, even if the hardness of the second fastened member and the hardness of the first fastened member are equal, the fastening axial force N causes the protrusions 4c to fall, and some of the protrusions 4c dig into the second fastened member (digging-up effect), thereby increasing the slip resistance.

[0019] Furthermore, because the dividing surface 5 is surrounded by the protrusions 4c, the binding force between the first and second fastened members 1 and 2 can be strengthened against external input F in any direction. Furthermore, at the point where the direction L in which the sliding load is applied intersects with the corner of the dividing surface 5 (L1 shown in Figure 2), the presence of an edge improves effectiveness. Furthermore, because the dividing surface 5 is formed uniformly and with regularity in the X-axis and Y-axis directions, the binding force can be further strengthened.

[0020] Next, a comparative experiment was conducted in which the first fastened member 1 was made of an aluminum alloy (A) and the second fastened member 2 was made of three different materials (B): (I) iron, which has a higher hardness than the aluminum alloy (A) (hardness: A < B), (II) an aluminum alloy with the same hardness (hardness: A = B), and (III) cationic paint, which has a lower hardness than the aluminum alloy (A) (hardness: A > B).

[0021] Furthermore, for the three types of materials, the fastening surface 1a of the first fastened member 1 was processed in the following four states, and comparative experiments were conducted: a: As processed by M / C b: Irradiated with the laser of the present invention (laser width: 0.06 mm, spacing: 0.03 mm) c: Irradiated with the laser of the present invention (laser width: 0.02 mm, spacing: 0.01 mm) d: Wet-blasted

[0022] The first fastened members 1 and the second fastened members 2 were fastened with bolts 3, and the slippage load (slip load) was measured. The results are shown in Figure 5. Note that laser irradiation was performed only on the fastening surface 1a of the first fastened members 1, and the test conditions (including axial force) were the same for each test.

[0023] As a result, as shown in Figure 5, in all materials (I), (II), and (III) of the second fastened member 2, i.e., regardless of the hardness of the second fastened member 2, the materials b and c, in which the fastening surface 1a was irradiated with the laser of the present invention, had a higher slippage load and increased slip resistance compared to the material a, which was left as it was after M / C processing.

[0024] Furthermore, for all materials (I), (II), and (III) of the second fastened member 2, the slippage load was higher and the slip resistance increased for the fastening surface 1a of type c, which had a closer laser width and spacing, than for type b.

[0025] Furthermore, compared to item d, which was subjected to wet blasting, items b and c, which were irradiated with the laser of the present invention, were superior. In item d, which was subjected to wet blasting, the uneven surface formed on the fastening surface 1a had no regularity, and it was not possible to apply a high binding force, whereas items b and c, which were irradiated with the laser of the present invention, were able to generate a large number of multiple protrusions 4c evenly, and it was found that a high binding force could be applied when the first fastened member 1 and the second fastened member 2 were fastened together.

[0026] Next, an embodiment in which the fastening structure of the present invention is applied to a vehicle knuckle is shown in Figure 6. The knuckle 11 (the first fastened member of the present invention) supports the axle of a rear wheel and includes a main body 12 that rotatably supports the rear wheel, upper arm connectors 13, 13, lower arm connectors 14, trailing arm connectors 15, 15, control arm connectors 16, 16, and disc brake connectors 17, 17.

[0027] The knuckle 11 is made of an aluminum alloy, and a connecting portion 21a of an upper arm 21 (a second fastened member of the present invention) is fastened and fixed to the inside of the bifurcated upper arm connecting portions 13, 13 with a bolt 22. A plurality of grooves (not shown) are formed on the opposing fastening surfaces 13a, 13a of the upper arm connecting portions 13, 13 by laser irradiation, and the plurality of grooves are formed so as to intersect with the direction in which a sliding load is applied by an external input. When irradiating the fastening surface 13a with a laser, tilting the knuckle 11 or moving the lens on the laser side allows for good laser irradiation of the fastening surface 13a.

[0028] The upper arm 21 is formed of a metal material, such as iron or an aluminum alloy, and the connecting portion 21a is inserted inside the upper arm connecting portions 13, 13 and comes into contact with the fastening surfaces 13a, 13a.

[0029] The upper arm connecting portions 13, 13 and the upper arm 21 are fixed by inserting and fastening bolts 22 through bolt holes 13b, 13b formed in the upper arm connecting portions 13, 13 and bolt holes 21b formed in the connecting portion 21a. At this time, multiple protrusions formed on the fastening surfaces 13a, 13a by laser irradiation come into contact with the upper arm 21 and collapse, or the collapsed protrusions dig into the upper arm 21, thereby increasing the slip resistance of the upper arm connecting portions 13, 13 and the upper arm 21 and strengthening the restraining force against external input.

[0030] Next, a description will be given of another embodiment in which the fastening structure of the present invention is applied to a vehicle compliance bracket 31. The compliance bracket 31 (first fastened member of the present invention) is a bracket attached to a lower arm (not shown), and includes a cylindrical portion 31a into which a bushing 32 is press-fitted, and two connecting arms 31b, 31c. The cylindrical portion 31a with the bushing 32 press-fitted therein is attached to the lower arm with a mounting bolt 33.

[0031] The compliance bracket 31 is made of an aluminum alloy, and one connecting arm 31b is fastened to a connecting portion 41a (a second fastened member of the present invention) of the vehicle body 41, while the other connecting arm 31c is fastened to a connecting portion 51a (a second fastened member of the present invention) of the subframe 51. A plurality of grooves (not shown) are formed by laser irradiation on a fastening surface 31d of one connecting arm 31b and a fastening surface 31e of the other connecting arm 31c. The plurality of grooves are also formed so as to intersect with the direction in which a sliding load is applied by an external input.

[0032] One connecting arm 31b and the connecting portion 41a of the vehicle body 41 are fixed by overlapping the connecting arm 31b and the connecting portion 41a, inserting bolts 61 into bolt holes 31f formed in the connecting arm 31b and bolt holes 41b formed in the connecting portion 41a, and fastening them together. At this time, multiple protrusions formed on the fastening surface 31d by the laser irradiation come into contact with the connecting portion 41a of the vehicle body 41 and collapse, or the collapsed protrusions bite into the connecting portion 41a, thereby increasing the slip resistance of the connecting arm 31b and the connecting portion 41a and strengthening the restraining force against external input.

[0033] The other connecting arm 31c and the connecting portion 51a of the subframe 51 are fixed by overlapping the connecting arm 31c and the connecting portion 51a, and inserting bolts 62 into bolt holes 31g formed in the connecting arm 31c and bolt holes 51b formed in the connecting portion 51a and fastening them together. At this time, multiple protrusions formed on the fastening surface 31e by laser irradiation come into contact with the connecting portion 51a of the subframe 51 and fall over, or the fallen protrusions bite into the connecting portion 51a, thereby increasing the slip resistance of the connecting arm 31c and the connecting portion 51a and strengthening the restraining force against external input.

[0034] In recent years, with the shift to electric vehicles, vehicle weights have tended to increase, and the external load on each fastening point increases in strength parts such as knuckles and compliance brackets as in the above-mentioned embodiments. Therefore, by applying the fastening structure of the present invention, the restraining force of each fastening point can be strengthened and misalignment of the two members can be suppressed, thereby ensuring stable driving of the electric vehicle.

[0035] The fastening structure and fastening method of the present invention are not limited to applications to strength components used in EV vehicles as in the above-described embodiments, but can be widely applied to fastening structures and fastening methods for a first fastened member made of an aluminum alloy and a second fastened member made of a metal material.

[0036] DESCRIPTION OF SYMBOLS 1...first fastened member, 1a...fastening surface, 1b...bolt hole, 2...second fastened member, 2a...bolt hole, 3...bolt, 4...groove portion, 4a...first groove portion, 4b...second groove portion, 4c...projection, 5...partition surface, 11...knuckle, 12...main body portion, 13...upper arm connecting portion, 13a...fastening surface, 13b...bolt hole, 14...lower arm connecting portion, 15...trailing arm connecting portion, 16...control arm connecting portion, 17...disc brake connecting portion , 21...upper arm, 21a...connecting portion, 21b...bolt hole, 22...bolt, 31...compliance bracket, 31a...cylindrical portion, 31b...one connecting arm, 31c...other connecting arm, 31d, 31e...fastening surface, 31f, 31g...bolt hole, 32...bush, 33...mounting bolt, 41...vehicle body, 41a...connecting portion, 41b...bolt hole, 51...subframe, 51a...connecting portion, 51b...bolt hole, 61, 62...bolt

Claims

1. A fastening structure comprising: a first fastened member made of an aluminum alloy; a second fastened member made of a metallic material; and a fastening member that fastens the first fastened member and the second fastened member together; wherein the fastening surface of the first fastened member facing the second fastened member has a plurality of grooves that intersect with the direction in which a sliding load is applied; and a plurality of protrusions that protrude toward the second fastened member are formed on the edges of the grooves, and the protrusions come into contact with the second fastened member when fastened.

2. The fastening structure according to claim 1, characterized in that the fastening surface is divided into a plurality of divided surfaces by the grooves extending in a plurality of directions.

3. The fastening structure according to claim 2, wherein the dividing surfaces are formed with regularity.

4. A fastening structure according to any one of claims 1 to 3, characterized in that the first fastened member is a knuckle for a vehicle.

5. A fastening structure according to any one of claims 1 to 3, characterized in that the first fastened member is a compliance bracket for a vehicle.

6. A fastening method for fastening a first fastened member made of an aluminum alloy to a second fastened member made of a metallic material using a fastening member, the method comprising: forming a plurality of grooves that intersect with the direction of the sliding load by irradiating the fastening surface of the first fastened member facing the second fastened member with a laser; and applying an axial force perpendicular to the fastening surface to the first fastened member and the second fastened member using the fastening member.

Images